An internal combustion engine generates a driving force by rotating a crank shaft with the aid of a so-called 4-stroke operation which consists of an intake stroke, a compression stroke, an ignition stroke or an explosion stroke determined by means of a fuel spray, and an exhaust stroke by using a mixed fuel or air. The piston descends during the explosion stroke, so the crank shaft connected to a connecting rod rotates by receiving a driving force. The exhaust-intake-compression strokes are consequentially performed as the piston descends by means of an inertia rotation of the crank shaft.
In the conventional art, various methods are proposed in order to more enhance the intake and exhaust efficiencies in such a manner that the diameters of intake and exhaust valves are made larger or the numbers of the same increase.
However, according to the above methods, the mechanism of a 4-stroke internal combustion engine becomes disadvantageously complicated. Since the diameter of a cylinder is generally determined at an initial designing stage, and an intake manifold and an exhaust manifold are separately configured from each other for the exclusive uses of each manifold, there is a limit for increasing the diameters of intake and exhaust valves and the numbers of the same due to the limited sizes of each intake and exhaust port.